This invention relates to a system and method of evaluating a turbine component and, more specifically, to a system and method of determining a total profile efficiency loss for a steam turbine component due to its surface conditions.
A steam turbine is often used to rotate a rotor in an electrical power generator. In particular, steam obtained by operation of a boiler may be directed along a steam flow path by a nozzle against a plurality of turbine blades, or buckets, connected to the rotor. The rotor is rotated within a stator by the steam flowing against the buckets to generate electrical power.
Abrasive materials are often carried by the steam as it flows through the turbine. These abrasive materials cause erosion of turbine components such as sealing strips, buckets and nozzles which are located along the steam flow path. Erosion of some of these turbine components result in excessive clearances being formed, often leading to increased steam leakage in the turbine. In addition to abrasive materials causing erosion of turbine components, the steam often carries contaminates which may deposit and collect on turbine components located along the steam flow path. These deposits of contaminates increase the surface roughness of the turbine components and may actually disturb the desired flow pattern of the steam.
The erosion of some turbine components and the collection of deposits on other turbine components are merely two examples of the many types of deterioration that may develop on the surfaces of turbine components after extended (e.g., ten years) operation. The operational efficiency losses of the steam turbine increase as the surface conditions of the turbine components deteriorate. In particular, the heat needed to enable the electrical generator to produce a given amount of electricity increases as the operational efficiency losses of the steam turbine increase.
In order to combat operational efficiency losses of the turbine, a service technician conducts a steam path audit. During the steam path audit, the service technician observes the surface conditions of turbine components located along the steam flow path for erosion, contaminate deposits and/or other signs of deterioration. This audit may be periodically scheduled for, for example, every five years of operation of the steam turbine.
A service technician typically determines a total profile efficiency loss for a turbine component in the steam flow path as a result of the judgments he/she reaches during the steam path audit. A determination on whether to repair or replace one or more of the turbine components can be made based on the judgments. However, the judgments reached are highly subjective and depend on the skill and experience level of the technician. The judgments may thus vary widely from technician to technician. Moreover, the judgment is “broad-brushed” in that a total profile efficiency loss for the entire turbine component is determined based on an evaluation of a single (local) surface location of that turbine component and a loss efficiency curve for that single surface location.
There thus remains a need to calculate the total profile efficiency loss of turbine components located along a steam path in a more accurate and repeatable fashion. That is, it would be beneficial to minimize the widely variable conclusions from different technicians evaluating the same turbine component and to increase accuracy of the total profile efficiency loss calculation by considering multiple surface conditions at different respective surface locations of the same turbine component. Exemplary embodiments of the present invention resolve these and other needs.